This application relates to the supply of high pressure cooling air to a blade outer air seal through an outer diameter chamber.
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion. The fan also delivers air into a compressor where air is compressed and then delivered into a combustor. The air is mixed with fuel and ignited in the combustor. Products of this combustion pass downstream over turbine rotors driving them to rotate. The turbine rotors, in turn, rotate compressor rotors and the fan rotor.
As can be appreciated, many components in the turbine section see very high temperatures. Two such components would be the turbine blades and blade outer air seals. Blade outer air seals typically sit radially outwardly of the blades and maintain clearance to increase the efficient use of the products of combustion.
One type of blade outer air seal is a so-called self-acting clearance control blade outer air seal. In such a blade outer air seal, two components formed of different materials having different coefficients of thermal expansion combine to control the expansion of the blade outer air seals to, in turn, control the clearance with the blade.
Both the blade and the blade outer air seal are provided with cooling air.
Traditionally, a turbine rotated at the same speed as the fan rotor. More recently, it has been proposed to include a gear reduction between a fan drive turbine and the fan rotor. With this change, the pressures and temperatures seen across the turbine sections have increased.
Thus, to drive cooling air into the turbine, the cooling air must be at a higher pressure than in the past. The highest pressure in the gas turbine engine is that downstream of a high pressure compressor. However, this cooling air is also at relatively high temperatures.
Thus, it has been proposed to tap high pressure air from a location downstream of the high pressure compressor and pass it through a heat exchanger prior to being delivered to the turbine section for cooling.
It has also been proposed to tap lower pressure from a more forward station in the compressor. The air is ducted to a separate auxiliary compressor and one or more heat exchangers to increase pressure and decrease the temperature of the air.